Power conversion systems play a significant role in converting energy produced by alternate energy sources, such as photovoltaic (PV) arrays and wind converters, into an optimized power form for supply to the electric grid or for conditioning power from the grid for driving a load. Insulated-gate bipolar transistor (IGBT) inverters, which include metal-oxide-semiconductor field-effect transistor (MOSFET) devices, are often essential components in any power conversion system. In these power conversion systems, IGBT control is critical to optimizing output power.
Power conversion systems are used to generate desired output alternate current (AC) output to a load or supply generated electricity to a utility grid. Certain power conversion systems include a single channel converter and inverter combo power module. A converter module of the single channel converter and inverter combo power module converts input AC current to DC current, and an inverter module of the single channel converter and inverter combo power module converts the DC current back to AC current for output to the load or the utility grid.
Multiple single channel converter and inverter combo power modules can be used to convert multiple phase AC current. Multiple single channel converter and inverter combo power modules can be combined in parallel to form a parallel converter system. The parallel converter system shares the electricity from each individual channel to increase the overall power output of the power conversion system and optimize the power efficiency of the power conversion system.
Each individual channel in the parallel converter system has provisions so that it can be turned on or off independently. However, as one of the channels in the parallel converter system is turned on or off when all the channels are sharing the output equally, such action may cause a shock to the parallel converter system as well as the output load. Hence, it is necessary to increase or decrease the participation of a channel in supplying the total output gradually when switching, thereby requiring that a given power channel be capable of supplying a portion of the total output other than what it would be when the parallel channels are sharing exactly equally. Such a capability is also useful when it is necessary to reduce the output of a channel and increase the output of another channel due to reduction in available channel cooling capability.
Furthermore, it is also essential to realize identical common mode voltages at the output of all parallel channels in a converter, irrespective of its main output voltage to prevent circulation of common mode currents among the parallel channels in the power converter.